1. Field of the Invention
The present invention relates to a probe card used to test the conduction of semiconductor chip circuits and LCD circuits.
2. Description of the Related Art
In the processes of manufacturing semiconductor devices or LCD glass bases (hereinafter referred to as LCD bases), a probing test is conducted in order to check circuits for disconnection or electrical characteristics. For example, a probing test machine (hereinafter referred to as a prober) is used in a probing test on semiconductor chip circuits. The prober comprises a loading/unloading section and a test section. The loading/unloading section is provided with a prealignment stage. The test section is provided with a wafer stage, and a probe card.
As shown in FIG. 1, the conventional probe card 6 is fitted with a number of probes 7 which are made of tungsten or Au--Cu alloy. The probe card 6 is fixed the frame of the prober, and the wafer stage 5 is located right under the card. A chip 3 is observed through apertures 6a of the probe card by means of an optical position sensor, such as a microscope 8 or CCD camera (not shown), and each pad 4 is aligned with the distal end of its corresponding probe 7, as shown in FIG. 2. This aligning operated is referred to as teaching. Based on the teaching, the stage 5 is moved in the X, Y, Z, and 8 directions, so that each pad 4 is brought into the distal end of its corresponding probe 7, as shown in FIG. 3. Electric current is supplied to the circuit through the probes 7, and signals from the circuit are delivered to the tester. Based on the test signals, the tester discriminates the conformity of the IC chip.
Modern semiconductor devices have a tendency toward higher-integration versions, such as 16- and 64-megabit versions, so that the pads 4 in each chip are as many as several hundreds. Each of pads 4 has a square top surface with each side of 60 to 100 .mu.m. Accordingly, the pads are arranged close to one another, that is, the pitches between the pads are extremely short. The pitch is distance of 100 to 200 .mu.m. Thus, the probes 7 to be attached to the probe card 6 must be considerably increased in number, e.g. several hundred, so that the layout of the probes is very difficult.
In large-scale integrated circuits, such as VLSIs and ULSIs, or Gate-Array formed by converting standard cells into composite chips, the pads 4 are arranged in the central region of the chip 3 as well as the peripheral regions thereof. Therefore, the VLSI, ULSI, and composite-chip ICs cannot be tested by means of the probe card 6 of the conventional type. This results because the array of the probes 7 is laid out so that the probes cannot be in contact with those pads 4a in the central region of the chip, although they can be in contact with the pads 4 in the peripheral region of the chip.
In some conventional probe cards, probes are arranged doubly on an insulating substrate in order to effect a probing test on the VLSI and the like. In these double-type probe cards, however, hundreds of probes having the end diameter of about 60 & L m must be mounted on the substrate, so that the mounting accuracy is critical. Also, the manufacture of the probe cards of this type requires manual operations, thus entailing high costs.
Meanwhile, it is necessary to ensure reliable electrical contact with the pads of semiconductor chips or LCD bases. For example, the wafer stage 5 is over-driven in the Z direction to press the pads 4 against the probes 7 so that the respective distal ends of the probes 7 bite in some measure into an oxide film of the upper surfaces of the pads 4, individually. In the high-integration chips, such as the VLSIs, however, there are differences in level or indentations between the pads, and the conventional metallic probes cannot cope with these indentations. More specifically, the probes bite too deep into high-profile pads, and cannot enjoy satisfactory contact with low-profile pads. Thus, the conventional probe cards cannot execute a reliable probing test.
According to the conventional probe cards, moreover, only one chip can be handled in each cycle of the probing test. Therefore, it takes a lot of time to test a wafer having a hundred chips or more.
On the other hand, each LCD base, which is larger than each semiconductor chip, cannot be tested at a time by means of the conventional probe card. Therefore, the probe card is moved to test the LCD at several portions. In this case, the pads on the LCD base and the probes must be aligned when the probe card is moved to each portion of the LCD. Obviously, examination of an LCD base requires a long time. Since the LCD bases recently developed have increased sizes, (e.g., 450.times.450 mm) it takes a very long time to accomplish a probing test on them. It is therefore demanded that an inexpensive probe card be provided which can have its contactors held in stable and uniform contact with the pads of a LCD base, respectively.